Hydrocracking process

ABSTRACT

A TWO-STAGE HYDROCRACKING PROCESS IN WHICH A HYDROCARBON CHARGE STOCK WHICH MAY CONTAIN MORE THAN 1000 P.P.M. NITROGEN IS HYDROCRACKED IN A FIRST STAGE CONTAINING A SULFIDED NICKEL TUNGSTEN ON A SUPPORTED COMPOSED OF AT LEAST ONE AMORPHOUS INORGANIC OXIDE AND A MODIFIED CRYSTALLINE ZEOLITE AND THAT PORTION OF THE PRODUCT BOILING ABOVE THE MOTOR FUEL RANGE IS HYDROCRACKED IN A SECOND STAGE CONTAINING A NOBLE METAL CATALYST.

United States Patent f 3,562,144 HYDROCRACKING PROCESS Edward T. Child, Fishkill, and Donald A. Messing, Wappingers Falls, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed June 24, 1968, Ser. No. 739,183 Int. Cl. Cg 13/02, 37/02 U.S. Cl. 208-59 10 Claims ABSTRACT OF THE DISCLOSURE This invention is concerned with the conversion of hydrocarbon oils. More specifically it is concerned with the hydrocracking of heavy hydrocarbon oils into lighter products. In a more specific aspect, it is concerned with the simultaneous production of high octane motor fuel and high quality jet fuel simultaneously from higher boiling hydrocarbon oils.

The hydrocracking of petroleum oils has been known for many years and was practiced although not too successf-ully in Europe several decades ago. However with the development of new catalysts and new operating techniques, it has been improved to the stage where it has attained commercial significance and is now being used in many refineries. In the early days of its commercial use, hydrocracking was designed exclusively for the production of motor fuel or gasoline. Currently with the increased demand for jet fuel, which can no longer be met by straight run kerosene, attempts have been made to adapt hydrocracking of heavy oils to the production of jet fuel as well as the production of motor fuel. Unfortunately, the sophisticated present day jet engine requires specific characteristics in a jet fuel just as the spark ignition engine requires specific characteristics in a motor fuel.

The characteristics of high quality jet fuel are substantially different from those of high octane motor fuel, the prime difference being that aromatics are a desirable component of motor fuel because of their high octane rating whereas such materials are extremely undesirable in a jet fuel as they contribute to a low luminosity number in the jet fuel. It is therefore hardly possible to subject a heavy oil such as a gas oil to hydrocracking and to recover from the product a low aromatic jet fuel having a high luminometer number and also to recover from the same product a highly aromatic motor fuel having a high octane number. If a hydrocracking unit is designed and operated to produce high octane gasoline then the jet fuel fraction of the product is of inferior quality and similarly if the hydrocracking unit is designed and operated to produce high luminometer number jet fuel then the gasoline fraction is not of high quality.

3,562,144 Patented Feb. 9, 1971 "ice It is an object of the present invention to provide a novel hydrocracking process. Another object is to provide a process for the simultaneous production of motor fuel and jet fuel in the same hydrocracking unit. Another object is to provide a novel method of operating a hydrocracking unit. Still another object of the invention is to provide a two-stage hydrocracking process in which different catalysts are used in each stage. Another object is to provide a process for the hydrocracking of hydrocarbon oil charge stocks having high organic nitrogen contents. These and other objects of the invention will be obvious to those skilled in the art from the following disclosure.

According to our invention there is provided a hydrocracking process for the simultaneous production of motor and jet fuels from heavy hydrocarbon oils which comprises passing the heavy hydrocarbon oil under hydrocracking conditions including a temperature of 600850 F. into contact in a first stage with a hydrocracking catalyst comprising sulfided nickel and tungsten on a support composed of at least one amorphous inorganic oxide and a modified crystalline alumino-silicate having uniform pore openings between 6 and 15 angstrom units and having an alkali metal content not greater than 1.0 wt. percent, separating a gasoline fraction from the efiluent, passing that portion of the eflluent boiling above the gasoline range into contact in a second stage with a hydrocracking catalyst comprising a noble metal on a cracking support under hydrocracking conditions including a temperature of 500700 F. and recovering from the efiluent from the second stage a fraction boiling in the jet fuel range.

The charge stocks used in the process of our invention include heavy petroleum hydrocarbon oils, such as straight run gas oil, fluid catalytically cracked cycle gas oil, atmospheric residuum, shale oil, tar sand oil, delayed coker gas oil and mixtures thereof and the like. As distinguished from the processes of the prior art, it is not necessary that the charge to the process of our invention be free from or low in nitrogen content. Our process is adapted to a hydrocracking charge stock not previously subjected to hydrotreating and is capable of handling charge stocks containing 100, 200 and even 500 or more p.p.m. nitrogen regardless of whether or not the nitrogen is in the form of ammonia or organic nitrogen over prolonged periods of time without rapid deactivation of the catalyst.

The hydrogen used in the process of our invention need not necessarily be pure. The hydrogen content of the hydrogenating gas should be at least about 60% and preferably is at least about by volume. Particularly suitable sources of hydrogen are catalytic reformer by-product hydrogen and hydrogen produced by the partial combustion of hydrocarbonaceous material followed by shift conversion of CO removal. Hydrogen rates are expressed in terms of standard cubic feet per barrel of charge to the reactor, viz. s.c.f.b.

The catalyst used in the first stage of our process contains two components, a hydrogenating component supported on a cracking component. The hydrogenating component comprises nickel and tungsten in sulfide form.

The cracking component of the catalyst comprises a mixture of a modified crystalline zeolite and at least one amorphous inorganic oxide, the modified zeolite being present in an amount between about 15 and 60% by weight. Suitable amorphous inorganic oxides are those displaying cracking activity such as silica, alumina, magnesia, Zirconia and beryllia which may have been treated with an acidic agent such as hydrofluoric acid to impart cracking activity thereto. A preferred mixture of amorphous inorganic oxides comprises silica-alumina in a proportion ranging from 69-90% silica and 10-40% alumina.

The modified zeolite portion of the cracking component has uniform pore openings of from 6-15 angstrom units, has a silica-alumina ratio of at least 2.5, e.g. 3-10, and has a reduced alkali metal content. The modified zeolite is prepared by subjecting synthetic zeolite Y to ion exchange by contacting the zeolite several times with fresh solutions of an ammonium compound at temperatures ranging between about 100 and 250 F. until it appears that the ion exchange is substantially complete. The ion exchanged zeolite is then washed to remove solubilized alkali metal and dried at a temperature sufficiently high to drive off ammonia. This converts the zeolite Y to the hydrogen form and reduces the alkali metal content to about 2-4 weight percent. The ion exchanged zeolite is then calcined at a temperature of about 1000 F. for several hours. After cooling, the ion-exchanged calcined zeolite is subjected to additional ion exchange by contact several times with fresh colutions of an ammonium compound and again washed and dried. This treatment results in a further reduction in the alkali metal content of the zeolite to less than 1% usually to about 0.5%. It would appear that after the first calcination, it is possible to engage in further ion exchange with the removal of additional alkali-metal ions not removable in the initial ion exchange. Calcination at e.g. 1000-1500 F. may take place here or it may be postponed until after the incorporation of the amorphous inorganic oxide and impregnation with the hydrogenating component at which time the composite should be calcined. Whether calcination is postponed or repeated, the final calcination temperature should not exceed 1200 F.

Hydrocracking catalysts containing a hydrogenation component supported on a cracking component composed of at least one amorphous inorganic oxide and the twice ion exchanged, twice calcined zeolite have superior hydrocracking activity and additionally are more resistant to deactivation when brought into contact with nitrogen compounds and polycyclic aromatics. They also show good stability to steam. The hydrocracking catalyst should also be substantially free from rare earth metals and should have a rare earth metal content below 0.5 weight percent, preferably below 0.2 weight percent. It has been found that although rare earth metals are reputed to enhance the activity and stability characteristics of cracking catalysts, their presence in a hydrocracking catalyst has been found to be undesirable.

When the hydrogenating component of the hydrocracking catalyst is a noble metal as in the second stage, it should be present in an amount between 0.2 and 5.0% by weight based on the total catalyst composite. Preferably the noble metal is present in an amount between 0.5 and 2%. When the hydrogenating component comprises nickel in conjunction with tungsten, the nickel should be present in an amount between 2 and 10% and the tungsten present in an amount between about 5 and 30%. Particularly suitable catalysts are those containing between 0.5 and 1.0 weight percent noble metal and those containing between 5 and nickel and between and 30% tungsten. Specific examples of suitable catalysts are those containing 0.75 weight percent palladium or containing about 6% nickel and tungsten on a support made up of about 22% modified zeolite Y, 58% silica and 20% alumina.

The hydrogenating component is deposited on the cracking component by impregnating the latter with a solution of a compound of the hydrogenating component.

4 Such techniques are well known in the art and require no description here.

When used in the sulfide form the catalyst may be converted thereto by methods well known in the art such as by subjecting the catalyst at a temperature between about 400 and 600 F. to contact with a sulfiding agent, for example hydrogen containing 10-20% hydrogen sulfide or carbon disulfide.

In the first stage reactor, the temperature is generally maintained between about 600 and 850 F., the pressure between 200 and 10,000 p.s.i.g., the liquid hourly space velocity between 0.2 and 10 volumes of oil/volume of catalyst/hour, and the hydrogen rate between 1000 and 50,000 s.c.f.b. A preferred temperature range is 625750 F. Advantageously, the temperature will to a certain extent vary depending on the nitrogen content of the charge, the greater the nitrogen content, the higher the reaction temperature. The preferred pressure range is 500-3000 p.s.i.g. Other preferred conditions are a space velocity of 0.5-2 v./v./hr. and a hydrogn rate of 300010,000 s.c.f.b.

The effluent from the first stage is separated into a hydrogen-rich gaseous portion which may be recycled to the first stage. Advantageously to prevent the build-up of gaseous hydrocarbons a portion of the recycle stream may be removed and sufiicient make-up hydrogen supplied to compensate for the amount removed and that consumed in the hydrocracking reaction. It is also possible to treat the recycle hydrogen for the removal of hydrogen sulfide and ammonia to prevent the build-up of these materials in the recycle stream. The normally liquid portion of the first stage effiuent is fractionated into a gasoline or motor fuel fraction which is removed and the remainder may then be subjected to treatment in the second stage. When the charge to the first stage is residual fraction, for example, an atmospheric residuum, or if it contains at least about 1% Conradson Carbon Residue, for example, delayed coker gas oil, then the heavy fraction of the effluent boiling above about 850 F. is separated from the first stage effiuent and may be recycled to the first stage or withdrawn from the system.

The catalyst in the second stage is also a hydrocracking catalyst and contains as the hydrogenating component a noble metal, for example, platinum or palladium on a cracking support. Generally, as mentioned above, the noble metal will be present in an amount between 0.2 and 5% by weight based on the entire catalyst composite, a preferred amount being between 0.5 and 2.0% by weight. The cracking component may suitably comprise a mixture of inorganic oxides such as silica alumina or a composite of inorganic oxides and low alkali metal crystalline zeolite such as the support used in the catalyst of stage 1 or may be solely a low alkali metal crystalline zeolite.

The reaction conditions in the second stage are substantially the same as those in the first stage with the exception that the temperature is maintained within the range of about 500-700 F. and preferably between 525 and 650 F. The temperature should also be lower e.g. 50- F. below that in the first stage.

The effiuent from the second stage is separated into a hydrogen-rich stream which is recycled to the second stage or to the first stage through a common recycle system, if so desired'The balance of the second stage eflluent is fractionated to separate a gasoline fraction, a jet fuel fraction and a heavier than jet fuel fraction. When it is desired to emphasize the production of gasoline the heavier than jet fuel portion of the effluent from the second stage is recycled to the first stage but if the jet fuel is to be the main product then that portion of the effluent from the second stage boiling above the jet fuel range is recycled to the second stage.

The following example is submitted for illustrative purposes only and is not to be considered as a limitation on the invention.

EXAMPLE The charge stock in this example is a gas oil having a boiling range of 405-650 R, an API gravity of 32.7, a sulfur content of 0.68 weight percent and a nitrogen content of 1700 ppm. The cracking component of the first stage catalyst contains 22 weight percent modified zeolite, 56 weight percent silica and 22 weight percent alumina. The hydrogenating component is made up of 5.4% nickel and 15.3% tungsten by weight based on the entire catalyst composite. The second stage catalyst contains 0.6 weight percent palladium on the same cracking component as the first stage catalyst. Operating and yield data are tabulated below.

TABLE Temperature, F LHSV, v./v./l1r Pressure, p.s.i.g Hydrogen rate, SCFB Yields, stage 1:

01-05, wt. percent..- iC4/nO vol. percent- 105/110 vol. percent. -215 F., vol. percent 215-400 F., vol. percent-.- Total 04+, vol. percent Product quality:

0 -215 F. RON (+3 cc. TEL) 215-400 F. RON (+3 cc. TEL) Hydrocarbon type analysis, vol. perce Parafiins Cyclommfitnq Aromatics Yields, stage 2:

01-03, wt. percent iO4/nC4, vol. percent iC5/nC5, vol. percent O5235 F., vol. percent 235-295 F., vol. percent 295-510 F., vol. percent Product quality:

C 235 F. RON (+3 ce. TEL)" 235295 F., IRON (+3 cc. TEL) Paraflins, v01. percent Cycloparaflins, vol. percent Aromatics, vol. percent 295-510 F.

Smoke Point, mm Luminometer number Freezing p0int, F Aromatics, vol. percent 1 Research octane number.

We claim:

1. A process for the simultaneous production of motor and jet fuels from a heavy hydrocarbon oil containing more than 500 p.p.m. nitrogen which comprises passing the heavy hydrocarbon oil under hydrocracking conditions including a temperature of 600-850 F. into contact in a first stage with a hydrocracking catalyst comprising sulfided nickel and tungsten on a support composed of at least one amorphous inorganic oxide and a crystalline alumino-silicate having uniform pore openings between 6 and 15 angstrom units and having an alkali metal content not greater than 1.0 wt. percent, separating a gasoline fraction from the effluent, passing a portion of the efiluent boiling above the gasoline range into contact in a second stage with a hydrocracking catalyst comprising a noble metal on a cracking support under hydro cracking conditions including a temperature of 500700 F. and recovering from the effiuent from the second stage a fraction boiling in the jet fuel range.

2. The process of claim 1 in which the catalyst in the second stage comprises platinum.

3. The process of claim 1 in which the catalyst in the second stage comprises palladium.

4. The process of claim 1 in which the temperature in the first stage is higher than the temperature in the second stage.

5. The process of claim 1 in which the hydrocarbon oil charged to the first stage has a Conradson Carbon Residue of at least 1%.

6. The process of claim 1 in which the first stage catalyst has a rare earth metal content of less than 0.5 Wt. percent.

7. The process of claim 1 in which the modified crystalline zeolite is present in the support of the first stage catalyst in an amount between 15 and by weight of the support.

8. The process of claim 1 in which the composition of the cracking support of the second stage catalyst is the same as that of the first stage catalyst.

9. The process of claim 1 in which the modified zeolite of the support of the first stage catalyst has an alkali metal content of less than 0.5 weight percent.

10. The process of claim 5 in which a fraction of the first stage eflluent boiling above about 850 F. is recycled to the first stage.

References Cited UNITED STATES PATENTS 3,402,996 9/1968 Maher et a1.

3,267,022 8/1966 Hansford 208-111 3,132,087 5/ 1964 Kelley et al. 20860 3,140,253 7/1964 Plank et al 208 3,254,017 5/1966 Arey et a1. 20859 DELBERT E. GANTZ, Primary Examiner R. BRUSKIN, Assistant Examiner U.S. Cl. X.R. 208-1 11 

